There are many applications in which a transponder which can be carried by an animal for automatic identification of the animal would be useful. Typical uses include monitoring migratory patterns of wild animals, for studying their habits, and for providing automatic identification of domestic animals, for controlling automatic feeding devices and the like, and for verifying their identity, e.g., in connection with racehorses. Automatically operated transponders would also be useful in connection with the monitoring of laboratory animals, for a wide variety of experimental purposes.
The prior art shows a number of transponders which provide identification of animals. However, no prior art device of which the inventors are aware includes all the attributes which would be desirable. See, for example, Fathauer U.S. Pat. No. 3,541,995 which shows a transponder which can be affixed to an animal's collar or the like for identifying it as belonging to a particular class. The Fathauer device is relatively large and bulky and not suitable for identification of wild animals.
Particularly in connection with the tracking of the movements of wild animals, it is desirable that transponders be provided which are extremely small and which can be readily implanted in the animals. An implantable transponder offers the advantage that it is not susceptible to loss and does not impede the motion of the animal. In particular, it would be desirable to provide transponders which are implantable in animals without the requirement of surgical procedures. To this end, Jefferts et al. U.S. Pat. No. 3,313,301 shows injection of a length of wire having magnetic properties into as animal by means of a syringe or generally similar device. See generally Jefferts et al. U.S. Pat. Nos. 3,128,744, 4,233,964, 3,820,545 and 3,545,405.
The presence of an animal having had a sliver of wire implanted therein can be detected automatically by an inductive coil or the like; however, the animal cannot be specifically identified in such an arrangement. Thus, it is not possible to track the movements of an individual animal, but only of a large number of them. Jefferts et al. U.S. Pat. No. 4,233,964 shows a similarly implantable tag which has grooves formed into its outer surface such that an individual animal can be identified by x-raying it and analyzing the groove pattern. This is obviously a very awkward system in use and does not lend itself readily to automatic monitoring of the movements of specific animals.
The prior art also includes transponders which provide an indication of the identity of a particular animal upon interrogation by an automatic interrogator device. Animal identification thus does not require operator intervention. See Hanton et al. U.S. Pat. No. 4,262,632 which shows a transponder for retention in the second stomach of a ruminant animal. The Hanton et al. transponder is adapted to be interrogated by an interrogator, to receive all operating power from the interrogator by means of an inductive coupling, and to transmit an identification signal in response to the interrogation. Hanton et al. also teach that such a transponder can be suitably encapsulated in glass for durability, another important aspect of devices of this type. However, the transponder of Hanton et al. is stated to be approximately three-quarters of an inch in diameter by three inches long. Such a transponder can only be implanted in an animal by a surgical procedure or by causing the animal to swallow it, e.g., by use of a conventional veterinary "balling gun." Such a transponder is not suitable for use in connection with wildlife, since it would be unduly complicated to apply these procedures to a large number of animals, such as fish, whose migratory patterns are to be studied. Not only is the Hanton et al. transponder too large for convenient implantation by means of a syringe or an automatic machine such as shown in some of the Jefferts et al. patents, but it is physically too large to be implanted into a relatively small animal such as a fish, a laboratory mouse, or the like.
A need therefore exists in the art for a transponder which is small enough to be syringe- or machine-implantable into a relatively small animal such as a fish, yet which provides an identification of the individual animal when interrogated by a suitable interrogator, such that the movements of individual animals can be studied by means of interrogators which record the animal's position without the intervention of a human operator.
It is therefore an object of the invention to provide a transponder which provides identification of an individual animal when it is interrogated, yet which is small enough to be syringe- or machine- implantable into an animal such as a fish.
It will be appreciated by those of skill in the art that it is important that a transponder for animal identification be durable in service, and it is accordingly an object of the invention to provide a transponder which is durable and reliable in service over a period of years, yet which is syringe-implantable and which provides an identification of the specific animal when interrogated.
Certain prior art transponders have relied on batteries for transmission of the identification signal. Other prior art transponders are powered by the interrogator itself by way of an inductive coupling. This is shown in Hanton et al. However, no reference known to the applicants shows a syringe-implantable transponder which is adapted to be powered by means of an inductive coupling to an interrogator, nor one in which the transponder additionally transmits an identification of an individual animal, and to provide the same is therefore an object of the present invention.
It is an important object of the present invention to provide a system for the monitoring of the movements of individual, small animals, for studying their migration patterns and the like, in which recordation of the movements of individual animals is possible and in which the data recording the movement of the individual animals is compiled without operator intervention.
Apart from the fact that prior art transponders which transmit identification signals are too large to be useful in connection with small animals, if they are to be used in connection with animals other than ruminants, they must be implanted surgically.
One of the significant drawbacks of surgical implantation of transponders is cost. A further disadvantage is the likelihood of infection, particularly in the case of wild animals or pets which are desirably released immediately after the surgery. Surgery also disfigures the animal to some extent, which is undesirable in the case of valuable animals. Surgery is psychologically traumatic to owners of domestic animals. For similar reasons, identification of the animals by ear tags and the like, which is generally within the prior art, is undesirable in the case of valued domestic animals and pets. Such external devices are also subject to loss.
For all these reasons, the art seeks a new identification transponder which is implantable by syringe or the equivalent, without surgical procedures, such that the transponder can be implanted in a simple and speedy manner, in which the chance of infection is greatly reduced, as compared to surgical implantation, in which the disfigurement of the animal is limited to an imperceptible pin prick, as compared to a scar left by surgery or the consistent undesired presence of an ear tag or the like. To eliminate these difficulties and deficiencies of the prior art in favor of simple syringe implantation of a transponder which nevertheless is durable in service, which does not require a battery, and which provides an identification of the individual animal are therefore important objects of the invention.
As mentioned above, the prior art also shows machinery for automatically implanting identification tags into animals such as fish. See Jefferts U.S. Pat. No. 3,820,545 and Debrotnik et al. U.S. Pat. No. 3,369,525. While such machinery would appear to have some utility, it is considered desirable to provide a transponder which is implantable using a relatively conventional syringe, which is less bulky and better suited for use in the field. In particular, it is an object of one aspect of the invention to provide a conveniently prepackaged, sterile cannula and identification transponder combination, such that the individual implanting the transponders into animals can be provided with all the equipment needed in a single sterile package which is used on a one-time basis; the cannula then being simply disposed of. In this way, sterility is ensured and operator convenience is optimized.